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  1. #1

    Yamaha 2000 xl800 not revving past 4500rpm

    2000 yamaha xl800 not revving past 4500rpm when in water. Out of water it revs fine. Idles fine and accelerates to 4500 fine as well. Tried to adjust the high speed screws with no luck. I recently rebuilt the carbs after it was sitting for 5 years or so... filters were totally clogged, but I cleaned out everything good. The only thing I didn't touch was the jets in side, I did not pull them out. Has a primer on it and when I am full throttle I can use the primer to get it to its max rpm, but i have to be constanly pumping it or else it falls back down to 4500... I think I will take the carbs off and make sure the jets are all clean and not clogged, which I have read happens... Not sure if it would be the high speed jets over the high speed screw.. the low speed seems fine, but the low sped screws are frozen, don't think I want to mess with them if it works fine down low. Power valves close after the engine is shutoff.. Compression is 165/165, which is pretty good so ive read for these.. Any other suggestions, or does it sound like a carb issue with the jets and screws.. Thanks


  2. #2
    RIVERA RACING RIVERA RACING's Avatar
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    Your jets maybe clogged.

  3. #3
    One high speed jet had a little bit inside of it, not sure if it was solid or it was just gas, I could not see the full circle, but it was partly blocked, not sure if thats enough to affect the speed and fuel like whats going on.

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    RIVERA RACING RIVERA RACING's Avatar
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    Yess............that would do that..

  5. #5
    Quote Originally Posted by RIVERA RACING View Post
    Yess............that would do that..
    Cool, hopefully it works, is there a reason why it would work out of the water but not in? Needs more fuel in water cause of the extra force of the water?

  6. #6
    RIVERA RACING RIVERA RACING's Avatar
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    Because is it doesn't have a load...on the motor
    Quote Originally Posted by millvarine View Post
    Quote Originally Posted by RIVERA RACING View Post
    Yess............that would do that..
    Cool, hopefully it works, is there a reason why it would work out of the water but not in? Needs more fuel in water cause of the extra force of the water?

  7. #7

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    You answered your own question when you said using the primer gets you full rpms. The engine is starving for fuel because of those main jets being plugged to some point. I wouldn't run it until you clean the jets. The engine is running lean and you could fry the cylinders. For cleaning carbs on older cars, trucks, etc., I use Berryman's Dip. Auto part stores usually have it and sometimes Walmart. It comes in a gallon can and is different from the Berryman's carb spray. You soak the carb in it or any parts after disassembly and it will eat away anything but the aluminum, brass, metal, or casting of the carb. If there is any plastic, rubber, gaskets, paint, or anything that isn't some type of metallic substance, it will be gone. Never tried it on sand though.

  8. #8
    Ok carbs are totally clean, including jets, but it still wont gk above 4500 rpm, at WOT. If I go three fourths throttle itll go to 5k thats it.. tried opening power valves manually but it doesnt affect anything.. when I jse the primer itll jump to 7k rpm, but I dont wanna do that or else ill run it lean and its not steady 7k just a burst.. compression is 150/150.. are there teml sensors that could be bad on it holding it below 4.5k rpm, or does it sound like my screws need to be adjusted along with maybe differebt jets? I hear primer will make kt more lean, but would it affect it this much?, Thanks

  9. #9
    Update: here is the servo motor out of the water, I never disconnected it in the water when I was trying to test open and closed valves, it may have even resetting itself in the water. https://drive.google.com/file/d/0Bzz...ew?usp=sharing but as you see here its acting funny.. Maybe its bad and thats the reason why its not letting me go past 4k rpms let alone 5k unless I prime it real quick... maybe a mix between carb screws and valves.. and i apologize for the breathing, allergies.

  10. #10

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